1. Field of the Invention
The disclosed invention relates to the field of lifting mechanisms employed to lift loads vertically. More specifically, it relates to lifting systems wherein the total lifted load comprises relative heavy components of the lifting apparatus itself. Typical embodiments of the disclosed invention apply, but are not limited, to hydraulic lifts, hydraulic cranes and rod lifting hydraulic pumps used to extract fluids from deep subsurface formations.
A typical example of an embodiment of the invention is an elevator lift. The total load lifted by typical elevator lifts includes weights of the cargo car and the cables, in addition to the useful lifted payload of passengers or other cargo. Most frequently, the weights of the cargo car and the cables constitute a significant portion of the total weight. The energy spent on lifting these “dead weights” is pure waste since it is producing useless work.
Another example pertains to rod-lifting technology, applied in oil and gas wells to extract fluids from subsurface formations, using beam pumps (also known as “horse head” pumps). The total load lifted by a typical rod-lifting pump comprises the useful payload of the oil column in the well casing tube in combination with the weights of the moving parts of the pump, which include the downhole pump, the rod string that connects the downhole pump to the surface-mounted pump and certain other parts of the lifting apparatus. Similar to the example of the elevator lift, the energy spent to lift the components of the lifting apparatus in every pumping cycle is wasteful since it produces useless work. In an oil or gas well application, the energy waste is even more pronounced, since the weights of the lifting apparatus (rod string, downhole pump, etc.) are relatively big compared to the weight of the cargo load (the fluid column), making up to 75 percent of the total load in deep wells. The amount of wasted energy and the associated operating costs are directly related to the duty cycle speed and the depth of the well.
The disclosed invention introduces an efficient lifting mechanism, using built-in, light-weight, stored energy resources to offset the “dead weight” loads, thus limiting the use of external energy to the amount required to lift the useful payload only, namely the cargo payload of an elevator, or the fluid column of an oil well, as referred to in the aforementioned examples.
2. Description of Prior Art
Lifts and cranes are common lifting mechanisms, typically using platforms, cables and pulleys to move loads vertically. The total load that a typical lift or crane moves comprises the sum of the lifted payload (the useful load) and the weight of certain moving components of the lifting apparatus, such as the platform, cables and pulleys to which the payload is attached. In many of these common applications, the combined weights of the moving parts of the lifting apparatus form a significant percentage of the total lifted load. The energy spent to lift these components is clearly wasted since this amount of energy is not producing any useful work.
There is an economic need to develop an efficient lifting mechanism, which uses external energy only to lift the useful payload, while minimizing any amount of energy spent on lifting components of the lifting apparatus.
Applied in a variety of lifting mechanisms and methods, prior art has been utilizing the “counterweight” concept as a method to balance, thus offset, weights of moving components (also termed hereinafter as “dead weight”) of the lifting apparatus, thereby reducing its operating power consumption and increasing its efficiency.
The following fourteen issued patents and published patent applications are the closest prior art known to the inventor of this invention, relating to the field of the disclosed invention.    1. U.S. Pat. No. 269,994 issued to Walter M. Bailey on Jan. 2, 1883 for “Elevator” (hereinafter the “Bailey Patent”);    2. U.S. Pat. No. 4,715,180 issued to Alan H. Rosman on Dec. 29, 1987 and assigned to Dynamic Hydraulic Systems, for “Hydraulic Lift Mechanism” (hereinafter the “Rosman Lift Patent I”);    3. U.S. Pat. No. 4,801,126 issued to Alan H. Rosman on Jan. 31, 1989 and assigned to Dynamic Hydraulic Systems, for “Hydraulically Operated Lift Mechanism” (hereinafter the “Rosman Lift Patent II”);    4. U.S. Pat. No. 5,238,087 issued to Alfonso Garrido et al on Aug. 24, 1993 and assigned to Otis Elevator Company, for “Advanced Energy Saving Hydraulic Elevator” (hereinafter the “Garrido Patent”);    5. U.S. Pat. No. 5,901,814 issued to Leandre Adifon et al on May 11, 1999 and assigned to Otis Elevator Company, for “Hydraulic Elevator Having a Counterweight” (hereinafter the “Adifon Patent”);    6. U.S. Pat. No. 5,975,246 issued to Renzo Toschi on Nov. 2, 1999 and assigned to Otis Elevator Company, for “Hydraulically Balanced Elevator” (hereinafter the “Toschi Patent”);    7. U.S. Pat. No. 5,957,779 issued to Walter F. Larson on Sep. 28, 1999 for “Tower” (hereinafter the “Larson Patent”);    8. U.S. Pat. No. 6,662,905 issued to Carlos Alberto Sors on Dec. 16, 2003 for “Elevator which counterweight is also the plunger of the propelling fluid dynamic device which produces and controls the movements thereof” (hereinafter the “Sors Patent”);    9. U.S. Pat. No. 5,996,688 issued to Glenn Schultz et al on Dec. 7, 1999 and assigned to Ecoquip Artificial Lift, for “Hydraulic Pump Jack Drive System For Reciprocating an Oil Well Pump Rod” (hereinafter the “Schultz Patent”);    10. U.S. Pat. No. 4,762,473 issued to James Tieben on Aug. 9, 1988 for “Pumping Unit Drive System” (hereinafter the “Tieben Patent”);    11. U.S. Pat. No. 4,631,918 issued to Alan H. Rosman on Dec. 30, 1986 and its continuation U.S. Pat. No. 4,848,085, issued on Jul. 18, 1989 and assigned to Dynamic Hydraulic Systems, for “Oil Well Pumping System Or The Like” (hereinafter the “Rosman Pump Patents”);    12. U.S. Pat. No. 7,530,799B2 issued to Norris E. Smith on May 12, 2009 for “Long-Stroke Deep-Well Pumping Unit” (hereinafter the “Smith Patent”);    13. U.S. Pat. No. 6,213,722 issued to Davor J. Raos on Apr. 10, 2001 for “Sucker Rod Actuating Device” (hereinafter the “Raos Patent”);
Bailey's U.S. Pat. No. 269,994, issued in as early as 1883, discloses a hydraulic (water based) lifting system for elevators, comprising a single-acting lifting actuator reciprocating an elevator via a set of pulleys and cables, an accumulator acting as a counterweight, a hydraulic pump and hydraulic conduits. The pump is installed in-line between the counterweight accumulator and the lifting cylinder. Hydraulic fluid in the counterweight accumulator is constantly under pressurized gas. To lift the elevator, the pump directs pressurized flow from the counterweight accumulator to the cylinder. Moving in and out, the cylinder operates a set of pulleys and cables, from which the elevator is suspended, reciprocating the elevator up and down. The power delivered by the counterweight to the cylinder is sized to an average value between a nominal load up and a nominal load down. A main drive spins the hydraulic pump in the desired direction, reciprocating the elevator up and down by porting flow from the counterweight to the cylinder, or in the opposite direction, thus operating also as a flow directional valve. If the lifted load is greater than the nominal average, the pump augments an amount of power required to lift only the incremental load. Changing its rotation direction, the pump allows the cargo load to descend, now porting flow back to the counterweight accumulator, thus recharging it and readying the system for the next duty cycle.
Rosman's U.S. Pat. No. 4,715,180 discloses a hydraulic lift mechanism, comprising a single-acting lifting actuator reciprocating a load directly, or via a set of pulleys and cables, an accumulator acting as a counterweight, a hydraulic pump and hydraulic conduits. The pump is installed in-line between the counterweight accumulator and the lifting cylinder. Hydraulic fluid in the counterweight accumulator is constantly under pressurized gas. To lift the elevator, the pump directs pressurized flow from the counterweight accumulator to the cylinder. Moving in and out, the cylinder reciprocates a load directly, or via a set of pulleys and cables from which the load is suspended. The power delivered by the counterweight to the cylinder is sized to lift the “dead-load” plus an average value between a maximum “live-load” and a minimum “live-load”. A main drive spins the hydraulic pump in the desired direction, reciprocating the cylinder and the load up and down by porting flow from the counterweight to the cylinder, or in the opposite direction, thus operating also as a flow directional valve. If the lifted load is greater than the counterweight force, the pump augments an amount of power required to lift only the incremental load. Changing its rotation direction, the pump allows the cargo load to descend, now porting flow back to the counterweight accumulator, thus recharging it and readying the system for the next duty cycle. In another embodiment, a hydraulic motor, driving a drum and cable, is used instead of a hydraulic linear actuator.
Rosman's U.S. Pat. No. 4,801,126 discloses a hydraulic lift mechanism, comprising a dual-acting, three-volume actuator reciprocating a load via a set of pulleys and cables, an accumulator acting as a counterweight, a hydraulic pump, control valves and hydraulic conduits. The actuator comprises three tubular members, dividing its internal space into three volumes. The first volume is connected to a gas pressurized accumulator, providing a bias force extending the actuator, thus counterbalancing the “dead-load” plus a portion of the “live-load”. A closed-circuit variable displacement pump ports hydraulic fluid to the two other hydraulic volumes. Porting fluid to the second volume provides a force retracting the actuator, whereas porting fluid to the third volume provides a force extending the actuator and augmenting the counterweight extension force. According to this invention, “the capacity of the system is for a rated load which comprises a fixed dead-load component and a live-load component of unestablished magnitude, and in which the pressure of preloading fluid supplied from said accumulator to said first volume is preselected to balance said lift system with equal hydraulic pressure in both said lines where the live-load component is at a preselected level intermediate a zero live-load condition and a maximum live-load condition.” In reading this patent, it is unclear whether the first volume is using pressurized gas, or is it using fluid under pressure to provide the counterbalancing force; the detailed description of this patent implies that “ . . . The first of these volumes is identified A and is an annulus charged with gas pressure via connection 32 to the charged interior of leg structure 13. Gas pressure in volume A is always operative over the full annular area of piston 27, urging piston 27 in the direction opposed to the gravitational force of load . . . ”, whereas claim 1 speaks of “ . . . an accumulator for supplying fluid under substantially uniform preloading pressure to said first volume . . . ”. In addition, the preferred embodiment shown in FIG. 2 presents a risk of entrapping a sizable amount of air in the enclosed upper part of the third hydraulic volume during normal operation, which can cause severe degradation of performance and ultimately failure of the system. The invention disclosed herein introduces a substantial improvement over this patent by avoiding air entrapments in any of its hydraulic space.
Garrido's U.S. Pat. No. 5,238,087 discloses a hydraulic lifting system for elevators, comprising a double-acting hydraulic actuator and a counterweight mechanism to offset the weight of the elevator car. In a preferred embodiment, the lifting mechanism comprises a pulley and a rope wrapped around it, the elevator car suspended from one side of the rope and a counterweight mass suspended from the other end. the actuator attaches directly to the counterweight mass. The weight of the counterweight mass is equal to the combined weights of the elevator car and half the weight of the cargo load (termed as “the duty load”). To move the elevator upward, the actuator applies to the counterweight a force equal in size to half the weight of the cargo load, working in the same direction as the counterweight. To move the elevator downward, the actuator applies to the counterweight a force no greater than half the weight of the cargo load, working in the opposite direction. The patent discloses an additional embodiment, featuring a pulley system that acts as a stroke multiplier, creating a desired ratio between the stroke of the elevator and the stroke of the actuator. This patent utilizes the concept of an efficient and compact lifting system by using the gravity force of shear weights to counterbalance the dead weight of elevator cars.
Adifon's U.S. Pat. No. 5,901,814 discloses a hydraulic lifting system for elevators, comprising a single-acting hydraulic actuator and a counterweight mechanism to offset the weight of the elevator car. The lifting mechanism further comprises a pulley and a rope wrapped around it, the elevator car suspended from one side of the rope, its other end attached to a counterweight mass. The weight of the counterweight mass is equal to the weight of the elevator car. To move the elevator upward, the actuator applies to the counterweight a force equal to the weight of the cargo load, working in the same direction as the counterweight. The patent discloses alternative pulley embodiments that act as stroke multipliers, creating a desired ratio between the stroke of the elevator and the stroke of the actuator. This patent is using the gravity force of shear weights to counterbalance the dead weight of the elevator car apparatus.
Toschi's U.S. Pat. No. 5,975,246 discloses a hydraulic lifting system for elevators, comprising a first single-acting lifting ram reciprocating a load, a second single-acting ram acting as a counterweight, a hydraulic pump, a control valve and hydraulic conduits. The hydraulic pump and the control valve are installed in-line between the lifting ram and the counterweight ram. The hydraulic fluid in the counterweight ram is constantly pressurized by weights pressing on the ram's piston. To lift the cargo load the control valve directs pressurized flow from the counterweight ram to the hydraulic pump, which ports hydraulic fluid to the lifting ram, lifting the cargo load. The power delivered by the counterweight to the hydraulic pump is sized to generate sufficient power to lift the car (the dead weights) plus half the cargo load. An electric motor, driving the hydraulic pump, augments the power required to lift the balance of the cargo load, namely half of its weight. Changing the state of the control valve reverses the process, allowing the cargo load to descend, the pump now porting flow back to the counterweight ram and lifting the counterweight load, thus readying the system for the next duty cycle. This patent features alternative embodiments using a plurality of counterweight rams. It also features alternative embodiments of pulley and cable provisions, providing a diversity of preferable stroke and speed ratios between the drive and the cargo.
Larson's U.S. Pat. No. 5,957,779 discloses a hydraulic lifting system for lifting people in gondola cars to the top of amusement park towers. The lifting system comprises a vertically mounted long stroke hydraulic actuator and a pulley system that doubles the stroke and speed of the gondola cars relative to the actuator. This patent is using the gravity force of shear weights to counterbalance the dead weight of the actuator piston.
Sors's U.S. Pat. No. 6,662,905 discloses a hydraulic lifting system for elevators, comprising a dual-acting hydraulic actuator and a counterweight mechanism to offset the weight of the elevator car. In its preferred embodiment, the elevator is suspended from a cable wrapped over the top of a pulley. The other end of the cable is connected to the piston of a hydraulic cylinder mounted vertically in an elevator pier. When hydraulic flow is applied to the hydraulic ports of the actuator, the piston reciprocates in and out of the actuator's cylinder, lifting and descending the elevator. This patent is unique in using the weight of the piston as a counterweight. According to this patent, the weight of the piston is sized to approximately the weight of the elevator car plus about half of the weight of the cargo load. A hydraulic pump provides to the actuator additional power required to lift the remaining half weight of the cargo load. A variety of alternative embodiments suggests use of single-acting actuators, pneumatic power instead of hydraulics and integration of a hydraulic pump and valves into the piston-counterweight assembly. The feasibility and practicality of this concept may be limited by the ability to package a sizable counterweight mass inside the body of the actuator's piston.
Schultz's U.S. Pat. No. 5,996,688 discloses a counterweighted hydraulic lifting system for recovering fluids from subsurface formations. The system comprises a plurality of single acting hydraulic cylinders, mounted on top of a wellhead and connected via a rod string to a downhole pump. As the wellhead-mounted cylinder(s) reciprocate, they move up and down the rod string and the downhole pump, lifting a column of fluid from the well in every stroking cycle. A master cylinder powers the wellhead cylinder(s), providing hydraulic fluid and pressure via hydraulic conduits. The master cylinder comprises two coaxial cylinders in series, mounted to a common central bulkhead. A single piston reciprocates inside the master cylinder bore. The single piston comprises multi piston heads of similar diameter assembled to a single piston rod, dividing the cylinders into several functional chambers. The chambers are connected via hydraulic conduits to hydraulic power supplies, providing flow and pressure to reciprocate the piston. A first chamber is connected via a hydraulic conduit to a first utility port of a hydraulic pump, that when pressurized pushes the piston down, pushing hydraulic flow from the master cylinder into the wellhead cylinders, lifting the wellhead cylinders, the downhole pump and the column of fluid in the downhole bore. A second chamber in the master cylinder is connected via a hydraulic conduit to a second utility port of a hydraulic pump, that when pressurized pushes the piston up. As the piston moves up, hydraulic fluid from the wellhead cylinders is allowed to flow back into the master cylinder, allowing the wellhead cylinders and the downhole pump to descend and fill up for the next pumping cycle. A hydraulic accumulator, charged with gas, provides hydraulic pressure to a third chamber in the cylinder. The accumulator pressure is pushing on the master cylinder piston, thus intensifying the utility pressure in the wellhead cylinders, thereby acting as a counterweight force providing a consistent bias force upward to offset the dead weights of the rod string and the downhole pump. The multiple wellhead cylinders and the structure of multiple cylinders in series in the master cylinder make this lifting mechanism relatively complicated and costly due its great number of components, as well as cumbersome to build and assemble compared to embodiments of the disclosed invention.
Tieben's U.S. Pat. No. 4,762,473 discloses another counterweighted hydraulic lifting system for recovering fluids from subsurface formations. The system comprises a hydraulic dual cylinder system, wherein the cylinders are connected coaxially in series. A single piston, reciprocating inside the cylinders coaxial bores, connects to the rod string and the downhole pump. As the piston reciprocates, it is pumping fluid from the well. The single piston comprises multi piston heads of similar diameter, dividing the cylinders into several functional chambers. The chambers are connected via hydraulic conduits to hydraulic power supplies, providing flow and pressure to reciprocate the piston. A first chamber is connected via a hydraulic conduit to a first utility port of a hydraulic pump, that when pressurized pushes the piston up, lifting the downhole pump and the column of oil above it. A second chamber is connected via a hydraulic conduit to a second utility port of a hydraulic pump, that when pressurized pushes the piston down, enabling the downhole pump to descend and fill up for the next pumping cycle. A hydraulic accumulator, charged with gas, provides hydraulic flow to a third chamber in the cylinder, acting as a counterweight by providing a consistent bias force upward, thereby offsetting the dead weights of the piston, the rod string and the downhole pump. The structure of multiple cylinders in series makes this lifting mechanism very tall and its relatively great number of components makes it complicated to build and assemble compared to the disclosed invention. In addition, the uniform cylinder bore constrains the operating pressures in the functional chambers when trying to achieve the desired operating forces.
Rosman's U.S. Pat. No. 4,631,918 and its continuation U.S. Pat. No. 4,848,085 disclose a counterweighted hydraulic lifting system for recovering fluids from subsurface formations. The disclosed apparatus comprises a single-acting hydraulic cylinder, mounted on top of a wellhead and connected via a rod string to a downhole pump, an accumulator acting as a counterweight, a hydraulic pump and hydraulic conduits. As the wellhead-mounted cylinder reciprocates, it moves up and down the rod string and the downhole pump, lifting a column of fluid from the well in every cycle. These patents are based on the principles of the aforementioned Rosman's U.S. Pat. No. 4,715,180. A hydraulic pump is installed in-line between the counterweight accumulator and the lifting cylinder. Hydraulic fluid in the counterweight accumulator is constantly under pressurized gas. A main drive spins the hydraulic pump in the desired direction, reciprocating the cylinder up and down by porting flow from the counterweight to the cylinder, or in the opposite direction. To move the cylinder up, the pump directs pressurized flow from the counterweight accumulator to the cylinder. The power delivered by the counterweight to the cylinder is sized to enable lifting of the dead weights of the rod string and the downhole pump plus half the load of the fluid column above the downhole pump. The hydraulic pump augments an amount of power sufficient to lift only the incremental load of half the weight of the fluid column, thereby saving a considerable amount of power and energy. Changing its rotation direction, the pump allows the cargo load to descend, now porting flow back to the counterweight accumulator, thus recharging it and readying the system for the next duty cycle.
Smith's U.S. Pat. No. 7,530,799B2 discloses another counterweighted hydro-mechanical rod-lifting system for recovering fluids from subsurface formations. The system comprises a pulley mounted over the wellhead, having a cable wrapped over its top. The rod string is connected to one end of the cable and a counterweight is supended from its other end, counterbalancing the dead weight of the downhole pump and the rod string. The system comprises a vertically mounted dual pulley and a chain (or a belt), driven by a hydrostatic transmission. The pulleys are mounted at a certain distance from each other, with a chain wrapped around them. The lower pulley shaft is rotated by a hydraulic motor, driven by a hydraulic pump, while the upper pulley is rotating freely. As the hydraulic motor rotates the lower pulley, the chain reciprocates up or down rotating the upper pulley. The counterweight is provided by the gravity force of shear weights attached to the chain. As the lower pulley is commanded to rotate, the chain moves around the pulleys, moving the counterweight up or down along the linear span between the two pulleys. As the chain drives the counterweight up and down, the rod string and the downhole pump reciprocate accordingly, lifting a column of fluid on every upstroke. The load lifting capacity is determined by the counterweight and the torque capacity of the hydraulic motor. The direction and the speed of the lifted load are determined by the rotation direction and the speed of the hydraulic motor respectively.
Raos's U.S. Pat. No. 6,213,722 discloses another counterweighted lifting system for recovering fluids from subsurface formations. The system comprises a direct-drive linear electromagnetic motor, mounted vertically on a wellhead, its armature connected via a rod string to a downhole pump. As the motor's armature is commanded up and down, it reciprocates the downhole pump, lifting a column of fluid in every cycle. Almost every motion parameter of the device can be programmed to provide a desired pumping profile. A spring means counterbalances the weights of the stator, the rod string and the downhole pump. This patent sites helical springs, pneumatic or hydraulic accumulators as alternative embodiment of counterweight means.
Counterweighted (also known as “Counterbalanced”) lifting systems have been applied widely for decades. The novelty of the disclosed invention presents an exceptional compact light-weight mechanism, comprising a considerable fewer number of components, superior performance attributes, higher efficiencies and energy conservation advantages and superior reliability, durability and maintainability properties, demonstrating substantial improvement over prior art and other existing technologies. The improvements of the disclosed invention are specifically pronounced in applications characterized by sizable heavy lifting apparatus. Unlike many of prior art inventions, the disclosed invention is feasible and practical in a great variety of applications, covering a broad range from light to very heavy loads and long strokes.
Further novel features and other aspects of the present invention will become apparent from the following detailed description, discussion, figures and the appended claims.